Discussion of the Original Paper “Pseudo-Dynamic Active Response of Non-Vertical Retaining Wall Supporting c-ϕ Backfill” by Sima Ghosh and Richi Prasad Sharma: Geotechnical and Geological Engineering, DOI 10.1007/s10706-010-9321-9

Excerpt

The writers are greatly appreciated for presenting their study on the seismic active earth pressure from c-ϕ soil backfill on the retaining wall with an inclined back face. The study is based on the pseudo-dynamic approach that uses the concept of phase difference due to the finite shear wave propagation behind a retaining wall as presented originally by Steedman and Zeng (1990), and Zeng and Steedman (1993). The pseudo-dynamic approach has been adopted in a similar way also in some other recent studies on seismic active and passive earth pressure analyses (Choudhury and Nimbalkar 2005; Choudhury and Nimbalkar 2006; Ghosh 2007; Ghosh et al. 2008; Ghosh 2010; Shafiee et al. 2010a) considering that this approach idealises the dynamic nature of earthquake loading more appropriately than the method of idealisation adopted in pseudo-static approach of analysing the seismic active and passive earth pressures. It is noted that the initial analysis involving Eqs. 1–20 follows the analytical approach considering the equilibrium of forces on an assumed failure wedge (Fig. 1), which is similar to the pseudo static analysis. The readers should note that there are a few mistakes in Fig. 1. In Fig. 1, the symbol “A” refers to the top of the retaining wall; it does not refer to the point as indicated in Fig. 1b. In the discusser’s opinion, R and ϕ as shown in Fig. 1b and Fig. 1c should not be identical. In Fig. 1c, H and P should be replaced by H ₁ and P ₂ , respectively. This work differs from other published works dealing with pseudo-dynamic analyses of active earth pressure mainly because of consideration of the inclined back face of the wall; however, inclination has not been considered appropriately while expressing the total surcharge at the base of the tension crack zone. Since the back face of the wall is inclined, the expression (q + γH ₀ ) with q as the surcharge at the top of the backfill as shown in Fig. 1 is approximate, and therefore, Eq. (5) that gives the total surcharge loading Q at the base level of the tension crack has an error. In the list of symbol, Q is defined as the total surcharge acting on the top of the backfill, which contradicts its meaning as used in the text. …